In the medical industry, and other such diverse industries as construction and military applications, a coherent light source such as a laser is often used for alignment and/or targeting applications.
Laser light sources are often used as light beam generators in these applications in order to create light beams of sufficient brightness, narrowness, and depth of field. However, many generators of coherent light such as gas lasers are often larger and more expensive than incoherent light sources such as incandescent light bulbs. Furthermore, gas laser light sources require more power at typically higher voltages. These limitations spurred the relatively recent shift from gas lasers to diode lasers in the patient alignment field.
While gas lasers and diode lasers are available in a variety of visible light wavelengths, which are perceived by a user as a variety of colors, laser sources are dedicated to the generation of a single light wavelength. This is limiting in various targeting or alignment applications. The person or object at which the light beam is directed may have differing light reflectivity or absorption characteristics. Therefore, particular wavelengths or colors of light may be perceived with more ease or more difficulty depending upon the subject or target at which the light beam is directed.
Often in alignment or targeting applications, a cross or cross-hair of light beams is preferred to a point or line of light as a cross-hair provides an indication of alignment in two planes. When a cross-hair is desired, this may require the use of two coherent light source generators. Alternatively, a complex beam-splitting optical arrangement is required to direct the light along two optical paths, only to be realigned to form the cross-hair. These implementations only further contribute to the size and expense of the alignment or targeting device.